1. Field of the Invention
The present invention relates to a gas lighter comprising a safety ignition system, also referred to as "resistant to children", that is to say can not be ignited by a child of less than five years old.
2. Description of the Prior Art
A gas lighter generally comprises a reservoir for containing liquefied petroleum gases, a valve mounted on the reservoir permitting gas to leave the reservoir, an opening and closing system for the release of gas operated by a lever, a system of regulation of the release of gas as well as the ignition system. In a known way, the ignition system comprises a pyrophoric flint co-operating with a spark wheel and is frequently protected by a cap on the top of the lighter. The spark wheel is mounted on an axis between two thumb wheels which are attached to it. The spark wheel has a cylindrical shape and each of the thumb wheels comprises a disk having a diameter slightly greater than that of the spark wheel. The rims of the thumb wheels comprise unevenesses or teeth which make them rough. Thus, a user can easily operate the spark wheel with a finger or thumb, because the finger or thumb does not slide on the thumb wheels.
When the spark wheel, being in contact with the flint, is rotated by operation of the thumb wheels by a digit of the user, a spray of sparks is created and is followed by the action of the same digit against the gas opening lever which releases a quantity of gas. The spray of sparks ignites the gas, producing a flame which forms above the cap. This spray of sparks must be of a certain quantity and density to ignite the gas. If the spark wheel is moved too slowly or intermittently then sufficient sparks will not be produced to ignite the gas to create the flame.
Such a system requires a positive action on the part of the user to produce and maintain a flame and requires two independent movements one after the other--rotation of the spark wheel and action on the gas opening lever--to produce a flame.
However, it is desirable to increase the difficulty of operating such lighters so that children younger than five years old are not able to produce a flame with such lighters.
Lighters already exist providing a supplementary difficulty which must be overcome to produce a flame and several patents or patent applications describe such lighters. For example, patents U.S. Pat. No. 5,125,829, U.S. Pat. No. 5,002,482 or international patent applications WO 93/17282, WO 95/04247.
The lighters described in these publications comprise, compared to conventional lighters, a supplementary device making access to the thumb wheels of the spark wheel more difficult, or by blocking movement of the gas opening lever.
In this way, these lighters comprise a complex structure involving an increased cost of manufacture. Furthermore, the use of some of these lighters is complicated and requires a particular method of use. Even adults can find several difficulties in the operation of such lighters and need preliminary instructions. It is also possible for the safety device to be disabled so that the lighter operates as an ordinary non-child resistant lighter.
U.S. Pat. No. 5,096,414 concerns a lighter which does not contain thumb wheels fixed to the spark wheel, but two flat discs having a diameter greater than that of the spark wheel, and freely mounted to rotate about an axis corresponding to that of the spark wheel. In this case operation of the spark wheel is achieved directly by the flesh of the digit of the user, after deformation between the two free discs. However this lighter is difficult to light even for an adult because the flesh of the digit does not provide enough grip on the spark wheel to move it against the flint to generate a sufficient spray of sparks. The flesh of the finger is very variable from one user to another and although some users may be able to operate it effectively many other users are not.
U.S. Pat. No. 5,104,313 relates to a lighter in which the spark wheel is mechanically coupled to the thumb wheel when the user presses sideways on the thumb wheel against the action of a spring arranged between the thumb wheel and the spark wheel. The disadvantage with this lighter is that the mechanical coupling is only disengaged as long as the spring force is able to keep it disengaged. The small size of the spring and the small size of the elastomeric toric joint and its proximity to the heat of the flame will make it very difficult to ensure that the spring will retain the lighter in a child resistant state for the duration of the life of the lighter. It is likely that the spring parts will fail thus enabling the corresponding engaging parts of the mechanical coupling of the spark wheel and thumb wheel to engage thus making the lighter easy to ignite by a child. Furthermore a side force is required on the lighter. This is a departure from the normal operation of the lighter for an adult which will require preliminary instructions when the lighter is first used.